Variable condenser for tuning electric oscillating circuits



Sept. 1' 28 1926. 4 1,601,281

K. J. G. AHLSTRAND VARIABLE CONDENSER FOR TUNING ELECTRIC OSCILLATINGCIRCUITS Filed May 4:, 1926 Patented Sept. 28, 1926.

UNITED STATES PATENT OFFICE.

KARL JOHAN GERHARD AHLSTRAND, 0F STOCKHOLM, SWEDEN.

VARIABLE CONDENSER FOR TUNING ELECTRIC OSCILLATING CIRCUITS.

Application filed May 4, 1926, Serial No. 106,675, and in SwedenNovember 13, 1925.

The present invention relates to improvements in variable condensers fortuning electric oscillating circuits in which the rotatable spindlesupporting the movable plates and a fine tuning spindle are connected toeach other by means of a gearing device consisting of a wheel journalledon an eccentric which is supported by the fine tuning spindle and is infrictional engagement with a casing surrounding said wheel and beingsecured to the spindle supporting the movable plates. Variablecondensers having such a gearing device are described in my co-pendingapplication Serial No. 54,022, filed September 2nd, 1925.

The object of my present invention is to make the said gearing devicevariable and at the same time to simplify the device used for guidingthe wheel jonrnalled on the eccentric.

The invention consists, chiefly, in this that the eccentric is movablein radial direction whereby it is possible to change the relationbetween the circumference of the wheel and the circular path ofengagement of the casing surrounding said wheel and thus the ratio ofgear between the two spindles.

In the accompanying drawing I have shown one embodiment of my invention.

Fig. 1 shows an end view of a condenser. the gearing device being shownin section on line a-b of Fig. 2, and

Fig. 2 shows a horizontal section on line (Z of Fig. 1.

Referring to the drawing, 1 indicates the frame to which the fixedplates 1 of the condenser are secured. 2 indicates a rotatable spindlesupporting the movable plates 9 of the condenser. To the rear end ofsaid spindle is secured the one part 8 of a casing 3, i, thecircumferential portion of which is of wedge-shaped cross-section, as isclearly shown in Fig. 2. The two parts 3, 4 of which the casing iscomposed may be connected to each other, for instance, by threadedflanges 3" and 45 respectively, so that the distance between the wallsof the casing may be varied.

The spindle 2 is hollow and in the same is rotatably journalled a finetuning spindle 5 supporting an eccentric which in the construction formshown consists of a wire 6 of steel or other yielding materialprotruding a distance from the axle 5. The said wire 6 is disposed in alongitudinal groove 16in the spindle 5 and is at its inner end rigidlysecured to the spindle, for instance, by soldering. The wire is soarranged that its free end tends to move radially outwards from thegroove 16. The wheel 7 is disposed on the end of the wire 6 extend inginto the casing 3, 41-. Said "heel con sists of a solid disc of metal orother suitable material and to the same an arm 8 is secured whichextends through a slot 17 in the bottom 3 of the casing and is providedat its free end with a notch 12 engaged by a pin 13 secured to theframe 1. The spindle 2 supports a hand wheel 1st and the spindle 5 aknob 15.

The device works as follows. The wheel 7 is pressed by the wire 6 intoengagement with the walls of the casing 8, 4;, two opposite points ofthe edges of the wheel 7 engaging the conical portions of the walls ofthe said casing. By suitable choice of the pressure exerted by the wire6 a suitable friction between the wheel and the casing is obtained. Whenthe spindle 5 is rotated, the edges of the wheel will engage successively different points of the walls of the casing, i. e. thecircumference of the wheel will roll off itself along a circular path inthe casing, the diameter of which is determined by the thickness of thewheel 7 and the distance between the conical walls of the casing 3, 4;.This path is indicated in Fig. 1 by the dotted line 18. As the wheel 7is in connection with the fixed frame 1 through the arm 8 it will impartto the casing and the spindle 2 connectedthereto a rotary motion thesize of which is determined by the difference between the circular path18 and the circumference of the wheel 7. In the present case it is,however, possible to change the size of the path 18. This can be done byscrewing the cover t more or less towards the bottom 8, whereby thedistance between the conical side walls will be changed. This in itsturn is possible by the eccentric 6 being disposed yieldingly so thatthe eccentricity accommodates itself to the path of engagement for whichthe casing has been regulated. In this way every desired ratio of gearbetween nil and the maximum ratio of gear determined by the dimensionsof the device may be ob tained.

In the construction form shown the wheel the eccentric make a smalloscillatory rotating movement around its centre. The

- size of this movement depends on the length of the a m 8 and as aresult of said move ment the ratio of gear between the spindles 2 and 5is change'l continuilly during each revolution of the spindle Tr hen thewheel U 7 is in the position shown in the drawing, i. e. when the pointof engagement between the wheel and the casing is neares to the pin 13,the ratio of gear is smallest. From this point it increases continuallydu *ing half a revolution until said. point of engagenent has movel tothe opposite end posi and thus is at the greatest distance said pinDuring the following halt r v- OlllLlQll the ratio of near decreasesccntir ill ally until it at last when the revo ution is completed andthe wheel 7 has'returnce into its initial position has been reduced itsorginal value. Said variations of the ratio of gear which may be reducedby increasing the length of the arm 8 are in many cases of no practi -alimportance, but obviously it is desirable to be able to obviate thesame, it this can be done in a simple manner. ln the present case thisis possible without complicating the device in any way and withoutintroducing any new eles simply by placing; the hole or the T rig-agedby the eccentric 6 not in the centre of the wheel but slightly nearer tothe guiding pin 13 or that point of enc i. iii

whee

O ga ement ot' the wheel that gives the slow-- est ratio of gear. Herebya wheel 7 is obtained the radius of which counting to the noint ofengagement increases continually JO 1 g halt revolution of the spindle 5)OSlilOll shown in the drawing and 'ontinually in the same proportion"iol owinghalt revolution of said Thus the same result is reached wereused in each new point "'gement a wheel having HlOtllGl cirth n thatused in the foregoing M nient. As the path 18 reiins the some. variationof tie at o ol Q is obtained which is contrac to the i'arzation of theratio of near caused b the arm 8 P-y suitable choice of the n "tirot thehole ot' the whee T said in can be made the same i1 size and thui Addpensate each other so that a quit ratio of gear between the two SPldf-Sand s obtained.

)oviously the device described above may be varied as to their detailswithout deviating from the principle of the inven tion.

- denser for tuning elects the combination of es, a system of movable 3ting the said mova ii 1e tun'ng spmdle having; the of rotation as thefirst mentioned mg on the latter, an eccentric the said fine tuningspindle ovahle radially, a wheel jourl eccentric within the said :ase ngin frictional engagement and means for preventing the one i membersbeing in frictional enfrcm being rotated, substantially 1' the purposeset forth. In a variable condenser for tuning; elecoscillating circuitsthe combination of 1 tixed plates, a system of movplates, at spindlesupporting the said hie rtesa hue tuning, spindle havaxis of rotation asthe first- Tndlc, a casing on the latter, a I ing material hating itsone -urczl to the said line tuning 1 1, er tree end of said wire tendveoutwards from the axis of roi said fine tuning spindle, a wheel led onthe free end of the said wire the said casing and being in fricpgrn:rent therewith, and means for ing the one of said two membersherietional engagement it]: n being ro ubstant ally as and for thepurpose a variable condenser for tuning elecilating circuits thecombination or a )1? lined plates, a system of movz hie i, a hil oi'spindle supporting the said plates, a The tuning spindle rotat aolyjournalled in the said hollow spindle, rigidly secured to the latter intion thereto, a wire of yielding ving its one end rigidly secured finetuning spindle, the other free vire tending to move outwards ojtrotation of said fine tr": \lle. a wheel termed with an eccent A is .7 1m nr located, n ne loosely engage tnc ce end or" said wire, 1' re andwheel being within said casing in frictional cnth, an arm rigidlysecured wheel and means for guiding" said as to prevent the. said wheelfrom l otated, snbstantiall as and for the pi'r 'zosc set fofirh.

1 testimoir whereof I have JQFGUHtO subsci ioed my name.

KARL JOHAN GERHARD AHLSTRAND.

